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Ophthalmology – Dellen
A dellen is a localized, saucer-like thinning of the peripheral cornea, typically found near the limbus. It usually appears as a small, elliptical depression measuring about 2 × 1.5 mm and is characteristically aligned parallel to the limbus. Dellen are most commonly associated with adjacent elevation of paralimbal tissue, which disrupts the normal tear film distribution over the corneal surface.
The underlying mechanism involves localized dehydration of the cornea. Elevation of nearby tissue—such as from a pinguecula, pterygium, or surgical bleb—interferes with the normal spread of the tear film, particularly the oily layer. This leads to inadequate lubrication of a focal area of the cornea, resulting in stromal thinning without true tissue loss from inflammation or infection.
Clinically, patients may have a history of recent ocular surgery, such as trabeculectomy or strabismus surgery, or conditions that elevate tissue near the limbus. On slit-lamp examination, the dellen appears as an area of localized corneal thinning with a steep edge toward the cornea and a more gradual slope toward the limbus. The lesion may or may not stain with fluorescein. In some cases, the thinning can appear quite pronounced and may resemble a descemetocele, although there is typically no outward bulging.
Dellen are commonly associated with conditions that alter the ocular surface contour, including episcleritis, pinguecula, pterygium, subconjunctival hemorrhage, glaucoma filtering blebs, limbal tumors, and paralytic lagophthalmos. These conditions contribute to tear film instability and localized drying.
The differential diagnosis includes more serious causes of peripheral corneal thinning such as peripheral ulcerative keratitis, corneal ulcers, and Terrien’s marginal degeneration. Unlike these conditions, dellen are non-inflammatory and typically lack significant pain or infiltrate.
Management focuses on restoring adequate hydration to the cornea. First-line treatment includes frequent use of artificial tears during the day and lubricating ointment at night. In some cases, patching the eye for a short period can help restore moisture. Treating the underlying cause of tissue elevation is also essential. If there is concern for secondary infection, topical antibiotics may be added.
The prognosis is generally excellent, with most dellen resolving completely when treated promptly. However, if left untreated for a prolonged period, they may result in corneal scarring. Rarely, severe thinning can occur, potentially requiring surgical intervention. Follow-up within about a week is recommended to ensure resolution and prevent complications.
A dellen is a localized, saucer-like thinning of the peripheral cornea, typically found near the limbus. It usually appears as a small, elliptical depression measuring about 2 × 1.5 mm and is characteristically aligned parallel to the limbus. Dellen are most commonly associated with adjacent elevation of paralimbal tissue, which disrupts the normal tear film distribution over the corneal surface.
The underlying mechanism involves localized dehydration of the cornea. Elevation of nearby tissue—such as from a pinguecula, pterygium, or surgical bleb—interferes with the normal spread of the tear film, particularly the oily layer. This leads to inadequate lubrication of a focal area of the cornea, resulting in stromal thinning without true tissue loss from inflammation or infection.
Clinically, patients may have a history of recent ocular surgery, such as trabeculectomy or strabismus surgery, or conditions that elevate tissue near the limbus. On slit-lamp examination, the dellen appears as an area of localized corneal thinning with a steep edge toward the cornea and a more gradual slope toward the limbus. The lesion may or may not stain with fluorescein. In some cases, the thinning can appear quite pronounced and may resemble a descemetocele, although there is typically no outward bulging.
Dellen are commonly associated with conditions that alter the ocular surface contour, including episcleritis, pinguecula, pterygium, subconjunctival hemorrhage, glaucoma filtering blebs, limbal tumors, and paralytic lagophthalmos. These conditions contribute to tear film instability and localized drying.
The differential diagnosis includes more serious causes of peripheral corneal thinning such as peripheral ulcerative keratitis, corneal ulcers, and Terrien’s marginal degeneration. Unlike these conditions, dellen are non-inflammatory and typically lack significant pain or infiltrate.
Management focuses on restoring adequate hydration to the cornea. First-line treatment includes frequent use of artificial tears during the day and lubricating ointment at night. In some cases, patching the eye for a short period can help restore moisture. Treating the underlying cause of tissue elevation is also essential. If there is concern for secondary infection, topical antibiotics may be added.
The prognosis is generally excellent, with most dellen resolving completely when treated promptly. However, if left untreated for a prolonged period, they may result in corneal scarring. Rarely, severe thinning can occur, potentially requiring surgical intervention. Follow-up within about a week is recommended to ensure resolution and prevent complications.
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